The present invention relates to polymeric materials useful in mounting systems and tapes for joining elements, and more particularly, to laminates and methods of making laminates including layers or films of polymeric materials having mutual adhesive properties which enable repeated fastening and separating of elements. The present invention also relates to diaper fastening systems using such polymeric materials, laminates and tapes.
The terms "autoadhesive" and "autoadhesion" are used herein to indicate the self-adhesive or cohesive-adhesive properties of a polymeric material which enable films, layers or coatings thereof to be repeatedly adhered together by application of pressure at service or room temperature and separated. Such materials are also substantially non-adhesive with respect to many other materials. Service temperature is used herein in accordance with its ordinary meaning to indicate the intended temperature or temperature range of use for the autoadhesive by the end user.
Japanese patent, application SHO62-296409, dated Nov. 25, 1987, discloses a self-adhering composition comprising a styrene-ethylene-butylene-styrene (SEBS) block copolymer and a tackifier. The tackifier is present in an amount ranging from 15 to 60 parts by weight per 100 parts by weight of SEBS block copolymer. Disclosed tackifiers include polyterpene resins, terpene phenolic resins, cyclo-aliphatic saturated hydrocarbon resins, C.sub.5 and C.sub.9 petroleum resins and rosin materials. If less than 15 parts of tackifier are used, it is indicated that the autoadhesion is low. On the other hand, use of more than 60 parts of tackifier is indicated to yield increased adhesive strength and adhesion to other materials. Further, the adhesion strength increases with time.
Japanese patent application SHO60-207682, dated Sept. 18, 1985, discloses an SEBS block copolymer used with or without a tackifier to provide a pressure-sensitive adhesive for use in a dust control mat. The compositions of this patent are indicated in the above-noted Japanese patent application SHO62-296409 to lack autoadhesion properties or to yield an excessively soft elastomer.
U.S. Pat. No. 4,791,024 discloses elastomers of natural rubber or a blend of natural rubber and a synthetic rubber, such as butadiene-styrene rubber, having cohesive-adhesive properties. The patent teaches that curing and cross-linking of the elastomer should be limited to retain adhesive properties. The cohesive-adhesive elastomer is itself secured to an element or article by mechanical attachment such as stapling or by cementing with a solvent solution of natural rubber. Application of the elastomer to a cotton fabric or polyvinylchloride film carrier to make a tape is disclosed. To facilitate repeated separation, the patent also teaches the use of filler materials such as threads, gauzes or powders at the exposed surface.
U.S. Pat. Nos. 4,040,124 and 3,921,221 disclose cohesive-adhesive materials derived from aqueous dispersions or solvent solutions of natural rubber or synthetic rubber for use in closures for hospital gowns. These materials are indicated to be capable of adhering to or having an affinity for bonding only to themselves. Repeated sealing and separating of the closures as well as freedom from contamination are also disclosed. U.S. Pat. No. 3,574,864 teaches the use of an aqueous natural rubber latex with casein and tackifying resins to provide similar type closures for hospital gowns.
U.S. Pat. Nos. 4,042,732 and 3,937,683 teach the use of cohesive compositions which may be sealed by manual pressing in packaging applications. The compositions comprise aqueous dispersions of natural or synthetic rubber and polyalkylmethacrylate together with an inert particulate material. Styrene-butadiene rubber and carboxylated styrene-butadiene rubber are disclosed as useful synthetic rubbers. The patent discloses application of the cohesive compositions by conventional coating methods, e.g. gravure rollers, flexographic plates or air-knife doctoring techniques. Examples of suitable wrapping materials are plastic film, such as low and high density polyethylene and polypropylene films, cellulose film or paper.
U.S. Pat. No. 3,196,034 also discloses a cohesive-adhesive composition of natural rubber or styrene-butadiene rubber for use in tape for securing film on a reel.
Ethylene-propylene rubber and ethylene-propylene-diene rubber require the use of tackifiers to achieve tackiness and green strength in accordance with U.S. Pat. No. 3,402,140 and 3,536,653. Illustrative tackifiers include phenolic resins, coumarone-indene resins, terpene resins, butadiene-styrene resins, polybutadiene resins and hydrocarbon resins. Ethylene-propylene and ethylene-propylene-diene elastomers have been used in self-fusing tape applications upon incorporation of suitable resins such as glycerol esters of hydrogenated rosin, thermoplastic terpene resins, petroleum hydrocarbon resins and others as taught in U.S. Pat. Nos. 3,470,127, 3,684,644 and 4,071,652.
The type of diaper fastening system of particular interest herein is generally illustrated in U.S. Pat. No. 4,710,190 wherein pressure-sensitive adhesives are used with a reinforcing tape on an outer liquid-impermeable layer of a diaper to provide a "landing zone" to releasably receive the diaper fastening tabs when the diaper is fastened closed. Reinforcing tape is required because the outer liquid-impermeable layer is relatively fragile and easily torn or damaged. In such systems, one of the terminal ends of each tab and the reinforcing tape are affixed to the diaper at a "factory-joint" by the diaper manufacturer using adhesives or other means. The other terminal ends of the tabs are movable by the end user from a storage and transport position to a deployed position secured to the landing zone in a "user-joint." To that end, the tab or at least the deployable end thereof is provided with a pressure-sensitive adhesive.
An inherent problem in the foregoing diaper fastening systems using pressure-sensitive adhesive tabs is that of contamination of the surfaces of the user-joint. Dust, powder, greasy or oily residues and other foreign matter on either of the two surfaces which interface at the user-joint tends to limit its strength.